JP2020115185A - Heating device, fixing device, and image forming apparatus - Google Patents

Abstract

To provide a device in which even when heating elements to be power-fed are switched with the use of a contact switch, an electromagnetic noise due to arc discharge is not emitted during the operation of the contact switch, and a reduction in life due to wear of contacts does not occur.SOLUTION: A heating device has a plurality of heating elements 54b1 to 54b3, and comprises: the heating element 54b1; the heating element 54b2 and heating element 54b3 that have a length in a longitudinal direction shorter than the length of the heating element 54b1; a first contact 54d1 to which one end of the heating element 54b1 is connected; a second contact 54d2 to which one end of the heating element 54b2 and one end of the heating element 54b3 are connected; a third contact 54d3 to which the other end of the heating element 54b3 is connected; a fourth contact 54d4 to which the other end of the heating element 54b1 and the other end of the heating element 54b2 are connected; and an electromagnetic relay 57a that switches between a connection state and an open state of an electrical path between the second contact 54d2 and fourth contact 54d4.SELECTED DRAWING: Figure 8

Description

The present invention relates to a heating device, a fixing device, and an image forming apparatus, and relates to a fixing heater used in an image forming apparatus and a control circuit for controlling the fixing heater.

It is known that in a heating device using a ceramic heater as a heat source, the following phenomenon occurs when a recording paper having a width shorter than the length of a heating element (hereinafter referred to as small size paper) is conveyed. There is. That is, it is known that a phenomenon in which the temperature becomes higher in the heat-generating region and the non-paper-passing region of the heating element than in the paper-passing region (hereinafter referred to as non-paper-passing portion temperature rise). The heat generating region is a region where the heat generating element generates heat. The non-sheet passing area refers to an area of the heat generating area that is not in contact with the small size paper. The paper passing area refers to an area of the heat generating area that is in contact with the small size paper. The temperature rise in the non-sheet passing portion is also called the edge temperature rise. If the temperature rise due to the temperature rise of the non-sheet passing portion becomes too large, there is a possibility that the surrounding members such as the member supporting the ceramic heater may be damaged. Therefore, a heating device and an image forming apparatus, which are provided with a plurality of heating elements having different lengths and are capable of reducing the temperature rise in the non-sheet passing portion by selectively using the heating elements having a length corresponding to the width of the recording paper, are provided. Many suggestions have been made. For example, in Patent Document 1, it is disclosed that at least a part of electrodes of a plurality of heating elements that are provided on an insulating substrate and can be independently driven are made common to achieve effective use of the substrate. ing. Further, it has been proposed that the number of electrodes provided at both ends of the substrate be the same so that the connectors connected to the ends are made common and the heat distribution in the longitudinal direction of the ceramic heater is made uniform.

Japanese Patent Laid-Open No. 2001-100558

In the conventional example, a configuration in which a heating element to be supplied with power is switched by a contact switch (an electromagnetic relay having a c-contact configuration) is described. When the c-contact type electromagnetic relay is operated in the configuration of the conventional example, arc discharge occurs between the contacts of the relay. Normally, when operating the electromagnetic relay, the power supply to the heating element is stopped (the triac is made non-conductive). In the configuration of the conventional example, since there is a potential difference between the contacts of the electromagnetic relay in this state, the arc current flows through the capacitive components at both ends of the triac (such as stray capacitance of the wiring pattern and noise countermeasure parts placed at both ends of the triac). Is. When arc discharge occurs between the contacts of the electromagnetic relay, electromagnetic noise may be emitted to cause a problem of EMI, and the electromagnetic relay peripheral circuit may malfunction. Further, when arc discharge occurs between the contacts of the electromagnetic relay, contact wear occurs, which shortens the life of the electromagnetic relay and thus the life of the device.

The present invention has been made under such a circumstance, and even when a heating element for supplying power is switched using a contact switch, electromagnetic noise due to arc discharge is not radiated during operation of the contact switch, and the contact It is an object of the present invention to provide a device in which the life is not shortened due to wear.

In order to solve the problems described above, the present invention has the following configurations.

(1) A heating device having a plurality of heating elements, wherein a first heating element, a second heating element and a third heating element having a length in a longitudinal direction shorter than that of the first heating element, A first contact to which one end of the first heating element is connected, a second contact to which one end of the second heating element and one end of the third heating element are connected, and the third heat generation A third contact to which the other end of the body is connected, a fourth contact to which the other end of the first heating element and the other end of the second heating element are connected, the second contact and the A heating device, comprising: a first switching unit that sets an electrical path to the fourth contact to a connected state or an open state.

(2) A heating device having a plurality of heating elements, wherein a first heating element, a second heating element and a third heating element having a length in a longitudinal direction shorter than that of the first heating element, A first contact to which one end of the first heating element is connected, a second contact to which one end of the second heating element and one end of the third heating element are connected, and the third heat generation A third contact to which the other end of the body is connected, a fourth contact to which the other end of the first heating element and the other end of the second heating element are connected, the third contact and the And a third switching means for setting an electric path with the fourth contact to a connected state or an open state.

(3) A fixing device characterized by fixing the toner image on the recording material by the heating device described in (1) or (2).

(4) An image forming apparatus comprising: an image forming unit that forms a toner image on a recording material; and the fixing device described in (3) above.

According to the present invention, there is provided a device in which electromagnetic noise due to arc discharge is not radiated during operation of a contact switch and the life of the contact is not shortened even when the heating element to be fed is switched using the contact switch. can do.

Overall configuration diagram of the image forming apparatus of Examples 1 to 4 Control block diagram of the image forming apparatus of Embodiments 1 to 4 Schematic cross-sectional view of the vicinity of the central portion in the longitudinal direction of the fixing device of Examples 1 to 4. FIG. 3 is a diagram showing a heater and a heater control circuit according to the first embodiment. The figure which shows the heater and the current path of a heater control circuit described in Example 1. FIG. 3 is a diagram showing a heater and a heater control circuit according to a second embodiment. The figure which shows the heater and the current path of a heater control circuit described in Example 2. FIG. 3 is a diagram showing a heater and a heater control circuit according to a third embodiment. The figure which shows the current path of the heater and heater control circuit described in Example 3. The figure which shows the heater and heater control circuit described in Example 4. The figure which shows the current path of the heater and heater control circuit described in Example 4.

Embodiments of the present invention will be described with reference to the drawings.

In the following embodiment, when switching three power supply paths having three heating elements, a contact switch is used to switch one power supply path. A configuration will be described in which electromagnetic noise due to arc discharge is not radiated during operation of the contact switch even when the power supply path is switched using the contact switch, and the life of the contact is not shortened due to wear of the contact.
In addition, in a heating device having three or more heating elements, the number of electrodes (hereinafter, first to fourth contacts) provided at both ends of the substrate is the same. As a result, the connectors connected to both ends of the board are made common and the heat distribution in the longitudinal direction of the ceramic heater is made uniform.

[overall structure]
FIG. 1 is a configuration diagram illustrating an in-line type color image forming apparatus, which is an example of an image forming apparatus including the fixing device according to the first exemplary embodiment. The operation of the electrophotographic color image forming apparatus will be described with reference to FIG. The first station is a station for forming a yellow (Y) toner image, and the second station is a station for forming a magenta (M) toner image. Further, the third station is a station for forming a cyan (C) color toner image, and the fourth station is a station for forming a black (K) color toner image.

In the first station, the photosensitive drum 1a which is the image carrier is an OPC photosensitive drum. The photosensitive drum 1a is formed by laminating a plurality of functional organic materials, such as a carrier generation layer that sensitizes and generates charges on a metal cylinder, and a charge transport layer that transfers generated charges, and the outermost layer is an electrical layer. It has low conductivity and is almost insulating. The charging roller 2a, which is a charging unit, is brought into contact with the photosensitive drum 1a, and is not driven to rotate as the photosensitive drum 1a rotates, so that the surface of the photosensitive drum 1a is uniformly charged. A voltage in which a DC voltage or an AC voltage is superimposed is applied to the charging roller 2a, and discharge is generated from a nip portion between the charging roller 2a and the surface of the photosensitive drum 1a in a minute air gap on the upstream side and the downstream side in the rotation direction. As a result, the photosensitive drum 1a is charged. The cleaning unit 3a is a unit that cleans the toner remaining on the photosensitive drum 1a after transfer, which will be described later. The developing unit 8a, which is a developing unit, includes a developing roller 4a, a non-magnetic one-component toner 5a, and a developer coating blade 7a. The photosensitive drum 1a, the charging roller 2a, the cleaning unit 3a, and the developing unit 8a are an integral type process cartridge 9a that is detachable from the image forming apparatus.

The exposure device 11a, which is an exposure unit, is composed of a scanner unit or an LED (light emitting diode) array for scanning a laser beam with a polygon mirror, and irradiates the photosensitive drum 1a with a scanning beam 12a modulated based on an image signal. Further, the charging roller 2a is connected to a charging high voltage power source 20a which is a means for supplying a voltage to the charging roller 2a. The developing roller 4a is connected to a developing high voltage power source 21a which is a voltage supplying means for the developing roller 4a. The primary transfer roller 10a is connected to a primary transfer high voltage power source 22a which is a voltage supply means for the primary transfer roller 10a. The above is the configuration of the first station, and the second, third, and fourth stations have the same configuration. With respect to the other stations, parts having the same functions as those of the first station are designated by the same reference numerals, and the suffixes of the reference numerals are denoted by b, c, d for each station. In the following description, the subscripts a, b, c, d will be omitted unless a specific station is described.

The intermediate transfer belt 13 is supported by three rollers of a secondary transfer counter roller 15, a tension roller 14, and an auxiliary roller 19 as a stretching member. A force is applied to the intermediate transfer belt 13 by a spring only in the tension roller 14, so that an appropriate tension force is maintained on the intermediate transfer belt 13. The secondary transfer counter roller 15 is rotated by receiving a rotational drive from a main motor (not shown), and the intermediate transfer belt 13 wound around the outer periphery is rotated. The intermediate transfer belt 13 moves at substantially the same speed in the forward direction (eg, clockwise direction in FIG. 1) with respect to the photosensitive drums 1a to 1d (eg, counterclockwise rotation in FIG. 1). Further, the intermediate transfer belt 13 rotates in the arrow direction (clockwise direction), the primary transfer roller 10 is arranged on the opposite side of the photosensitive drum 1 with the intermediate transfer belt 13 interposed therebetween, and the intermediate transfer belt 13 moves. Followed by the rotation. The position where the photosensitive drum 1 and the primary transfer roller 10 are in contact with each other across the intermediate transfer belt 13 is called a primary transfer position. The auxiliary roller 19, the tension roller 14, and the secondary transfer counter roller 15 are electrically grounded. The primary transfer rollers 10b to 10d of the second to fourth stations have the same structure as the primary transfer roller 10a of the first station, and therefore the description thereof will be omitted.

Next, the image forming operation of the image forming apparatus of the first embodiment will be described. When the image forming apparatus receives the print command in the standby state, it starts the image forming operation. The photosensitive drum 1, the intermediate transfer belt 13 and the like start to rotate in the arrow direction at a predetermined process speed by a main motor (not shown). The photosensitive drum 1a is uniformly charged by the charging roller 2a to which a voltage is applied by the charging high-voltage power source 20a, and then an electrostatic latent image according to image information is formed by the scanning beam 12a emitted from the exposure device 11a. To be done. The toner 5a in the developing unit 8a is negatively charged by the developer coating blade 7a and is coated on the developing roller 4a. Then, a predetermined developing voltage is supplied to the developing roller 4a from the developing high voltage power source 21a. When the photosensitive drum 1a rotates and the electrostatic latent image formed on the photosensitive drum 1a reaches the developing roller 4a, the electrostatic latent image is visualized by the negative toner adhering to the photosensitive drum 1a. A toner image of the first color (for example, Y (yellow)) is formed. The other color M (magenta), C (cyan), and K (black) stations (process cartridges 9b to 9d) operate in the same manner. An electrostatic latent image by exposure is formed on each of the photosensitive drums 1a to 1d while delaying a writing signal from a controller (not shown) at a constant timing according to the distance between the primary transfer positions of the respective colors. A DC high voltage having a polarity opposite to that of the toner is applied to each of the primary transfer rollers 10a to 10d. Through the above steps, the toner images are sequentially transferred to the intermediate transfer belt 13 (hereinafter referred to as primary transfer), and a multiple toner image is formed on the intermediate transfer belt 13.

Thereafter, in accordance with the formation of the toner image, the paper P which is the recording material loaded in the cassette 16 is fed (picked up) by the paper feed roller 17 which is rotationally driven by a paper feed solenoid (not shown). .. The fed paper P is conveyed to a registration roller (hereinafter referred to as a registration roller) 18 by a conveyance roller. The sheet P is conveyed to the transfer nip portion, which is a contact portion between the intermediate transfer belt 13 and the secondary transfer roller 25, by the registration roller 18 in synchronization with the toner image on the intermediate transfer belt 13. A voltage having a polarity opposite to that of the toner is applied to the secondary transfer roller 25 by the secondary transfer high-voltage power supply 26, and the multicolor toner images of four colors carried on the intermediate transfer belt 13 are collectively printed on the paper P (recording). (On the material) (hereinafter referred to as secondary transfer). The member (for example, the photosensitive drum 1) that has contributed until the unfixed toner image is formed on the sheet P functions as an image forming unit. On the other hand, the toner remaining on the intermediate transfer belt 13 after the secondary transfer is finished is cleaned by the cleaning unit 27. After the secondary transfer is completed, the paper P is conveyed to a fixing device 50 that is a fixing unit, receives the fixing of the toner image, and is discharged to the discharge tray 30 as an image formed product (print, copy). The fixing device 50 corresponds to the heating device of the present invention. The film 51, the nip forming member 52, the pressure roller 53, and the heater 54 of the fixing device 50 will be described later.

[Block diagram of image forming apparatus]
FIG. 2 is a block diagram for explaining the operation of the image forming apparatus, and the printing operation of the image forming apparatus will be described with reference to this figure. The PC 110, which is a host computer, is responsible for outputting a print command to the video controller 91 inside the image forming apparatus and transferring the image data of the print image to the video controller 91.

The video controller 91 converts the image data from the PC 110 into exposure data and transfers it to the exposure control device 93 in the engine controller 92. The exposure control device 93 is controlled by the CPU 94 to turn on/off the exposure data and control the exposure device 11. Upon receiving the print command, the CPU 94, which is the control means, starts the image forming sequence.

The engine controller 92 is equipped with a CPU 94, a memory 95, etc., and performs a preprogrammed operation. The high voltage power source 96 is composed of the charging high voltage power source 20, the developing high voltage power source 21, the primary transfer high voltage power source 22, and the secondary transfer high voltage power source 26 described above. The power control unit 97 includes a bidirectional thyristor (hereinafter referred to as a triac) 56, a heating element switch 57 that switches a heating element that supplies power, and the like. The power control unit 97 selects a heating element that generates heat in the fixing device 50 and determines the amount of power to be supplied. The drive device 98 is composed of a main motor 99, a fixing motor 100 and the like. The sensor 101 includes a fixing temperature sensor 59 for detecting the temperature of the fixing device 50, a paper presence sensor 102 having a flag for detecting the presence or absence of the paper P, and the detection result of the sensor 101 is transmitted to the CPU 94. The CPU 94 acquires the detection result of the sensor 101 in the image forming apparatus, and controls the exposure device 11, the high-voltage power supply 96, the power control unit 97, and the drive device 98. As a result, the CPU 94 forms an electrostatic latent image, transfers the developed toner image, fixes the toner image on the paper P, and the like, and in the image forming process in which the exposure data is printed on the paper P as a toner image. Take control. The image forming apparatus to which the present invention is applied is not limited to the image forming apparatus having the configuration described with reference to FIG. 1, it is possible to print the paper P having different widths, and has the heater 54 described later. Any image forming apparatus including the fixing device 50 may be used.

[Fixing device]
Next, the configuration of the fixing device 50 according to the first exemplary embodiment will be described with reference to FIG. Here, the longitudinal direction is a rotation axis direction of the pressure roller 53 that is substantially orthogonal to a conveyance direction of the sheet P described later. The length of the paper P in the direction (longitudinal direction) substantially orthogonal to the transport direction is called the width. FIG. 3 is a schematic sectional view of the fixing device 50.

The sheet P holding the unfixed toner image Tn from the left side of FIG. 3 is heated while being conveyed from the left side to the right side in the figure in the fixing nip portion N, so that the toner image Tn is fixed to the sheet P. The fixing device 50 according to the first exemplary embodiment includes a cylindrical film 51, a nip forming member 52 that holds the film 51, a pressure roller 53 that forms a fixing nip portion N together with the film 51, and a sheet P for heating. And a heater 54.

The film 51, which is the first rotating body, is a fixing film as a heating rotating body. In Example 1, for example, polyimide is used as the base layer. An elastic layer made of silicone rubber and a release layer made of PFA are used on the base layer. In order to reduce the frictional force generated between the film 51 and the nip forming member 52 and the heater 54 due to the rotation of the film 51, grease is applied to the inner surface of the film 51.

The nip forming member 52 plays a role of guiding the film 51 from the inside and forming a fixing nip portion N between the film 51 and the pressure roller 53. The nip forming member 52 is a member having rigidity, heat resistance, and heat insulation, and is made of liquid crystal polymer or the like. The film 51 is fitted onto the nip forming member 52. The pressure roller 53, which is the second rotating body, is a roller serving as a pressure rotating body. The pressure roller 53 includes a core metal 53a, an elastic layer 53b, and a release layer 53c. The pressure roller 53 is rotatably held at both ends, and is rotationally driven by the fixing motor 100 (see FIG. 2). Further, the film 51 is driven to rotate by the rotation of the pressure roller 53. The heater 54, which is a heating member, is held by the nip forming member 52 and is in contact with the inner surface of the film 51. The fixing temperature sensor 59 detects the temperature of the heater 54. The heater 54 will be described later.

[Heater and heater control circuit]
FIG. 4 shows a heater and a power control unit 97 which is a heater control circuit used in the heating apparatus of the first embodiment. FIG. 4A shows the heater 54 and the power control unit 97 used in the first embodiment, and FIG. 4B shows a pp′ cross section of the heater 54. The heater 54 is mainly composed of heating elements 54b1 to 54b3 mounted on a substrate 54a (on the substrate) formed of ceramic or the like, contacts 54d1 to 54d4, and a protective glass layer 54e such as insulating glass. The heating elements 54b1 to 54b3 are resistors that generate heat when supplied with power from an AC power supply 55 such as a commercial AC power supply. The contacts 54d1 and 54d2 are provided at one end of the substrate 54a in the longitudinal direction, and the contacts 54d3 and 54d4 are provided at the other end of the substrate 54a in the longitudinal direction. In this way, the number of contacts (electrodes) provided at both ends of the substrate 54a is made equal to two, for example. The protective glass layer 54e is provided to insulate the user from the heating elements 54b1 to 54b3 that have substantially the same potential as the AC power supply 55.

The heating element 54b1 which is the first heating element is a heating element mainly used when fixing the toner on the sheet P having the maximum width among the sheets P that can be conveyed in the heating device. Here, the width is a direction substantially orthogonal to the conveyance direction of the paper P, and is also the longitudinal direction of the heater 54. Therefore, the length (dimension) in the longitudinal direction of the heating element 54b1 is set to be several mm longer than the letter size width 215.9 mm. As shown in FIG. 4, two heating elements 54b1 are provided on the upstream side and the downstream side of the conveyance direction of the paper P (vertical direction in FIG. 4A), and two heating elements 54b2 and 54b3 are sandwiched on both sides of the substrate 54a. It is arranged. A heating element 54b2 and a heating element 54b3 are arranged in the area of the heating element 54b1 in the longitudinal direction of the substrate 54a. The heating element 54b1 is mainly used also when the heating device is started (that is, when the temperature is raised from the state where the heating device is cooled (the temperature is approximately the same as room temperature) to a predetermined temperature). Is. Therefore, the heating element 54b1 is designed so as to be able to supply necessary electric power when the heating device is activated. The heating element 54b1 is connected to the contact 54d1 which is the first contact and the contact 54d4 which is the fourth contact.

The heating element 54b2, which is the second heating element, is a heating element corresponding to the width of the B5 size, and the length of the heating element 54b2 in the longitudinal direction is set to be several mm longer than the width 182 mm of the B5 size. The heating element 54b2 is connected to the contact 54d2 and the contact 54d4 which are the second contact. The heating element 54b3, which is the third heating element, is a heating element corresponding to the width of A5 size, and the length of the heating element 54b3 in the longitudinal direction is set to be several mm longer than the width of 148 mm of A5 size. The heating element 54b3 is connected to the contact 54d2 and the contact 54d3 which is the third contact.

It is assumed that the heating elements 54b2 and 54b3 are used while the heating device is warmed to some extent, and the rated power of the heating elements 54b2 and 54b3 is set lower than the rated power of the heating element 54b1. That is, the heating element 54b1 is positioned as the main heater, and the heating elements 54b2 and 54b3 are positioned as the sub heaters. Therefore, the main heater (heating element 54b1) and the sub-heaters (heating elements 54b2, 54b3) are used while being switched, mainly at the time of startup and load fluctuation. In addition, the heater 54 includes three heating elements 54b1 to 54b3 having different lengths in the width direction of the sheet P. The purpose of this is to suppress the temperature rise in the non-sheet passing portion and to achieve high productivity even when a paper P having a width smaller than a letter size or A4 size (hereinafter referred to as a small size paper) is printed. Therefore, also from this viewpoint, the performance of the heater 54 is exhibited by frequently switching between the main heater (heating element 54b1) and the sub-heaters (heating elements 54b2, 54b3).

The contact 54d1 is connected to the first pole of the AC power supply 55 via a bidirectional thyristor (hereinafter referred to as a triac) 56a which is a first switch means. The contact 54d2 is connected to the first pole of the AC power supply 55 via the triac 56b which is the second switch means. The contact 54d3 is connected to the first pole of the AC power supply 55 via the triac 56c which is the third switch means. The contact 54d4 is connected to the second pole of the AC power supply 55 without passing through a triac or the like. The contact 54d2 and the contact 54d4 are connected via an electromagnetic relay 57a having an a-contact configuration which is a first switching means. The electromagnetic relay 57a brings an electrical path (power supply path) between the contact 54d2 and the contact 54d4 into a connected state (hereinafter, also referred to as a short-circuited state) or an open state. The electromagnetic relay 57a is not limited to the a-contact type electromagnetic relay, and a contact switch such as a b-contact type electromagnetic relay or a c-contact type electromagnetic relay may be used. Further, the electromagnetic relay 57a may use a non-contact switch such as a solid state relay (SSR), a photomos relay, or a triac.

[Power supply path]
FIG. 5 shows three types of current paths (electrical path and power supply path) to the heating elements 54b1 to 54b3 when the heater 54 and the power control section 97 of the first embodiment are used.

(Power supply to the heating element 54b1)
The electric current when the electric power is supplied from the AC power supply 55 to the heating element 54b1 flows through the route shown by the thick line in FIG. The temperature of the heater 54 is detected by a temperature detection element (not shown) such as a thermistor, and based on the temperature information, the triac 56a operates based on an instruction from a microcomputer (not shown) so that the heating element 54b1 reaches a predetermined temperature. Controlled to be. Power supply to the heating element 54b1 does not depend on the triacs 56b and 56c and the electromagnetic relay 57a having an a-contact configuration. That is, when power is supplied to the heating element 54b1, the electromagnetic relay 57a may be open or short-circuited. In FIG. 5A, the electromagnetic relay 57a is in an open state as an example.

(Power supply to the heating element 54b2)
The electric current when the electric power is supplied from the AC power supply 55 to the heating element 54b2 flows through the route shown by the thick line in FIG. 5B. When supplying power to the heating element 54b2, the contact of the electromagnetic relay 57a having the a-contact configuration is set to the open state. Since the contact impedance of the open-state a-contact type electromagnetic relay 57a is sufficiently higher than that of the heating element 54b2, almost no current flows through the a-contact type electromagnetic relay 57a, and only the heating element 54b2 can generate heat. The electric power supplied to the heating element 54b2 is controlled by the triac 56b.

(Power supply to heating element 54b3)
The electric current when the electric power is supplied from the AC power supply 55 to the heating element 54b3 flows through the route shown by the thick line in FIG. When power is supplied to the heating element 54b3, by setting the contact of the electromagnetic relay 57a having the a-contact configuration to be in a short-circuited state, almost all the current flows through the heating element 54b3. Since the contact impedance of the electromagnetic relay 57a having the a-contact configuration in the short-circuited state is sufficiently smaller than that of the heating element 54b2, almost no current flows through the heating element 54b2, and only the heating element 54b3 can generate heat. The electric power supplied to the heating element 54b3 is controlled by the triac 56c.

[Switching power supply path]
To switch between the power supply path to the heating element 54b1 (FIG. 5(a)) and the power supply path to the heating element 54b2 (FIG. 5(b)), the contact of the electromagnetic relay 57a having the a-contact configuration is opened in advance. Keep it. Switching between the power supply path (FIG. 5A) and the power supply path to the heating element 54b2 (FIG. 5B) can be independently controlled only by the contactless switches of the triac 56a and the triac 56b. .. Since the state can be changed only by the operation of the non-contact switch (=triac), the power supply path (Fig. 5(a)) and the power supply path (Fig. 5(b)) are frequently changed or the power is supplied. The path (FIG. 5A) and the power supply path (FIG. 5B) can be used together.

The same applies to the power supply path to the heating element 54b1 (FIG. 5A) and the power supply path to the heating element 54b3 (FIG. 5C). The contact of the electromagnetic relay 57a having the a-contact configuration is short-circuited in advance, and the path is switched by the control of the triac 56a and the triac 56b. Since the state can be changed only by the operation of the contactless switch (=triac), the power supply path (Fig. 5(a)) and the power supply path (Fig. 5(c)) are frequently changed or the power is supplied. The path (FIG. 5A) and the power supply path (FIG. 5C) can be used together.

On the other hand, when switching between the power supply path of the heating element 54b2 (FIG. 5B) and the power supply path of the heating element 54b3 (FIG. 5C), it is necessary to switch the state of the electromagnetic relay 57a having the a-contact configuration. .. Here, both ends of the electromagnetic relay 57a having an a-contact configuration are connected to both ends of the heating element 54b2. As a result, when the triac 56b is non-conducting, both ends of the electromagnetic relay 57a having an a-contact configuration have the same potential regardless of whether the electromagnetic relay 57a having an a-contact configuration is open or short-circuited. Therefore, during the operation of the electromagnetic relay 57a having the a-contact configuration (the electromagnetic relay 57a is operated when the triac 56b is non-conductive), arc discharge does not occur between the contacts of the electromagnetic relay 57a having the a-contact configuration. Therefore, electromagnetic noise is not radiated and contact wear (=life shortening) due to arc discharge does not occur. Thereby, although the power supply path (FIG. 5B) and the power supply path (FIG. 5C) are exclusive, the power supply path can be switched with a high degree of freedom.

By using the heater 54 and the electric power control unit 97 of the first embodiment, not only the electromagnetic noise emission and contact wear elimination during the operation of the electromagnetic relay but also the following effects can be obtained. First, since the number of electrodes (contact points) provided on both ends of the substrate 54a can be made the same, the connectors connected to both ends of the substrate 54a are made common and the heat distribution in the longitudinal direction of the ceramic heater is made uniform. Can be planned. Second, two of the three state transitions can be performed by controlling only the contactless switch. Therefore, the state transition affected by the operation wait of the contact switch (waiting for contact stabilization due to the contact bounce of the relay) can be minimized and the performance of the heater 54 can be maximized, so that the productivity of small size paper can be improved. ..
Note that, for convenience of description, a noise filter and an energy saving function for cutting off the noise filter and the like from the AC power supply 55 for energy saving are not shown, but the effect of the present invention can be obtained even if circuits necessary for these actual functions are provided. It doesn't change.

As described above, in the configuration in which the power supply path is switched by using the contact switch, it is possible to eliminate the life reduction due to electromagnetic noise emission from the contact switch and contact wear. As described above, according to the first embodiment, even when the heating element to be supplied with power is switched using the contact switch, electromagnetic noise due to arc discharge is not emitted during operation of the contact switch, and life reduction due to contact wear does not occur. A device can be provided.

[Heater and power controller]
FIG. 6 shows the heater 54 and the power control unit 97 used in the heating device of the second embodiment. The heater 54 used in the second embodiment is the same as that of the first embodiment, and therefore its explanation is omitted. The power control unit 97 of the second embodiment has a configuration in which the triac 56b and the triac 56c of FIG. 4 are combined and one triac 56b is used, and an electromagnetic relay 57b having a c-contact configuration that is the second switching means is provided instead. Has become. The present embodiment is characterized in that the electromagnetic relay 57b having the c-contact configuration has a role of selecting which heating element the triac 56b is connected to and a role of the electromagnetic relay 57b having the a-contact configuration of FIG. is there.

Specifically, the electromagnetic relay 57c having the c-contact configuration as the second switching means is connected to the contact 57c1 connected to the contact 54d2, the contact 57c2 connected to the triac 56b and the contact 54d3, the AC power supply 55 and the contact 54d4. The contact 57c3 is connected. When the contact 57c1 and the contact 57c2 are connected to each other, the electromagnetic relay 57c is in a state in which electric power is supplied to the heating element 54b2. The electromagnetic relay 57c is in a state in which electric power is supplied to the heating element 54b3 when the contact 57c1 and the contact 57c3 are connected. In the electromagnetic relay 57c, when the contact 57c1 and the contact 57c3 are connected, the contact 54d2 and the contact 54d4 are connected. Therefore, the electromagnetic relay 57c also functions as the first switching unit.

[Current supply path]
FIG. 7 shows three types of current supply paths to the heating elements 54b1 to 54b3 when the heater 54 and the power control section 97 of the second embodiment are used. The current when power is supplied from the AC power supply 55 to the heating element 54b1 flows through the route indicated by the thick line in FIG. The power supply from the AC power supply 55 to the heating element 54b1 is controlled by the triac 56a. When power is supplied to the heating element 54b1, the electromagnetic relay 57c may be in a state where the contacts 57c1 and 57c2 are connected or a state where the contacts 57c1 and 57c3 are connected.

The electric current in the case of supplying electric power from the AC power supply 55 to the heating element 54b2 flows through the route shown by the thick line in FIG. 7B. At this time, the electromagnetic relay 57c having the c-contact configuration is connected to the triac 56b and the contact 54d4 by connecting the contacts 57c1 and 57c2, and the triac 56b controls the power supply from the AC power supply 55 to the heating element 54b2. Since the contact impedance of the electromagnetic relay 57c having the c-contact configuration is sufficiently smaller than that of the heating element 54b3, almost no current flows through the heating element 54b3, and only the heating element 54b2 can generate heat.

The electric current when the electric power is supplied from the AC power supply 55 to the heating element 54b3 flows through the route shown by the thick line in FIG. 7C. At this time, the electromagnetic relay 57c having the c-contact configuration is connected to the contact 54d3 side by connecting the contact 57c1 and the contact 57c3, and the triac 56b controls the power supply from the AC power supply 55 to the heating element 54b3. Since the contact impedance of the electromagnetic relay 57c having the c-contact configuration is sufficiently smaller than that of the heating element 54b2, almost no current flows through the heating element 54b2 and only the heating element 54b3 can generate heat.

The electromagnetic relay 57c having the c-contact configuration short-circuits (Fig. 7(b)) and opens (Fig. 7(c)) the contacts 54d2 and 54d4 to short-circuit (Fig. 7(b)) and open (Fig. 7(b)). It has the first function of performing FIG. Further, the electromagnetic relay 57c having the c-contact configuration has a second function of short-circuiting (FIG. 7C) and opening (FIG. 7B) the heating element 54b3. That is, the electromagnetic relay 57c having the c-contact configuration is characterized in that it has both the first function and the second function.

Here, the contacts 57c1 and 57c2 of the electromagnetic relay 57c having the c-contact configuration are connected to both ends of the heating element 54b3. As a result, when the triac 56b is non-conductive, the contact 57c1 and the contact 57c2 have the same potential regardless of whether the contact 57c1 is open or short-circuited. Further, the contacts 57c1 and 57c3 of the electromagnetic relay 57c having the c-contact configuration are connected to both ends of the heating element 54b2. As a result, when the triac 56b is non-conducting, the contact 57c1 and the contact 57c3 have the same potential regardless of the open state or the short-circuited state. That is, when the triac 56b is non-conductive, the contacts 57c1, 57c2, 57c3 are all at the same potential. As a result, during the operation of the electromagnetic relay 57c having the c-contact configuration (the electromagnetic relay 57c is operated when the triac 56b is non-conductive), arc discharge does not occur between any of the contacts of the electromagnetic relay 57c having the c-contact configuration. Therefore, no electromagnetic noise is radiated when the electromagnetic relay 57c having the c-contact configuration is operated, and contact wear (life shortening) due to arc discharge does not occur.

The configuration of the second embodiment is synonymous with the functions of the electromagnetic relay 57a having the a-contact configuration and the triac 56c shown in FIG. 4 of the first embodiment being performed only by the electromagnetic relay 57c having the c-contact configuration. Therefore, by selecting the configuration of the second embodiment, it is possible to secure the same function as that of the first embodiment while further reducing the number of circuit components.

In the configuration of the first embodiment, if the triac 56b is in the conducting state and the contact of the electromagnetic relay 57a having the a-contact configuration is in a short state, that is, the output end of the AC power supply 55 is in a short state. In this case, it cannot be said that the current fuse (not shown) may be blown, and the device may be destroyed. On the other hand, in the configuration of the second embodiment, the output end of the AC power supply 55 is not short-circuited, and it can be said that the configuration is more reliable.

As described above, in the configuration in which the power supply path is switched by using the contact switch, it is possible to eliminate the life reduction due to electromagnetic noise emission from the contact switch and contact wear. In addition, it is possible to provide a device that is less expensive, space-saving, and highly reliable than that of the first embodiment. As described above, according to the second embodiment, even when the heating element that supplies power is switched using the contact switch, electromagnetic noise due to arc discharge is not emitted during operation of the contact switch, and the life of the contact is not shortened due to contact wear. A device can be provided.

[Heater and power controller]
FIG. 8 shows the heater 54 and the power control unit 97 used in the heating device of the third embodiment. The heating elements 54b1 and 54b3 of the heater 54 are the same as those in the first to third embodiments. The length in the longitudinal direction of the heating element 54b4, which is the second heating element, is the difference length between the heating element 54b2 and the heating element 54b3 of the heater 54 of the first to third embodiments. Two heating elements 54b4 are arranged on both sides of the heating element 54b3 in the direction orthogonal to the longitudinal direction. That is, the total length in the longitudinal direction of the heating element 54b4 and the length in the longitudinal direction of the heating element 54b3 are set to be the same as the length in the longitudinal direction of the heating element 54b2 of the heater 54. As will be described later, the heating element 54b3 and the heating element 54b4 may be regarded as one heating element and used. Therefore, it is necessary that the resistance values of the heating elements 54b3 and 54b4 per unit length in the longitudinal direction are set to be equal.

[Current supply path]
FIG. 9 shows three types of current paths to the heating element when the heater 54 and the power control section 97 of the third embodiment are used. The current when power is supplied from the AC power supply 55 to the heating element 54b1 flows through the route shown by the thick line in FIG. 9A. The power supply from the AC power supply 55 to the heating element 54b1 is controlled by the triac 56a. When supplying power to the heating element 54b1, the electromagnetic relay 57a may be open or short-circuited.

The current when power is supplied from the AC power supply 55 to the heating elements 54b3 and 54b4 flows through the route indicated by the thick line in FIG. 9B. At this time, the contact of the electromagnetic relay 57a having the a-contact configuration is set to an open state, and the current flows through the heating elements 54b3 and 54b4 in series. Hereinafter, the heating elements 54b3 and 54b4 connected in series may be referred to as a series heating element. As a result, both the heat generating element 54b3 and the heat generating element 54b4 generate heat, and in the longitudinal direction of the heater 54, heat can be applied to the same range as that of the heat generating element 54b2 of the first to third embodiments. It can be regarded as one heating element. The power supply from the AC power supply 55 to the series heating element of the heating element 54b3 and the heating element 54b4 is controlled by the triac 56b. Since the contact impedance of the electromagnetic relay 57a having the a-contact configuration in the open state is sufficiently larger than that of the heating element 54b4, current does not substantially flow through the electromagnetic relay 57a having the a-contact configuration, and only the heating elements 54b3 and 54b4 can generate heat. it can.

The current in the case of supplying power from the AC power supply 55 to the heating element 54b3 flows through the route shown by the thick line in FIG. 9C. At this time, the contact of the electromagnetic relay 57a having the a-contact configuration is set to the short-circuited state, and the triac 56b controls the power supply from the AC power supply 55 to the heating element 54b3. Since the contact impedance of the electromagnetic relay 57a having the a-contact configuration in the short-circuited state is sufficiently smaller than that of the heating element 54b4, almost no current flows through the heating element 54b4, and only the heating element 54b3 can generate heat. Here, both ends of the electromagnetic relay 57a having an a-contact configuration are connected to both ends of the heating element 54b4. Therefore, electromagnetic noise is not radiated during the operation of the electromagnetic relay 57a having the a-contact configuration as in the first embodiment, and contact wear (=life shortening) due to arc discharge does not occur.
In the configuration of the third embodiment, as the electromagnetic relay 57a, an electromagnetic relay having an a-contact configuration that is cheaper and smaller than the electromagnetic relay 57c having the c-contact configuration used in the second embodiment can be used. And there is a merit that it can be made small.

The heater 54 according to the third embodiment needs to be designed so that a step (discontinuity in heat distribution) does not occur in the heat distribution at the boundary between the two heating elements 54b3 and 54b4 in the longitudinal direction. .. In practice, it is desirable to devise the heating elements 54b3 and 54b4 at the two boundary portions to have, for example, a tapered shape.

It should also be noted that there are restrictions on the resistance values of the heating elements 54b3 and 54b4. The resistance value of the heating element 54b3 is R103, and the resistance value of the heating element 54b4 is R114. Since the resistance value Rs of the series resistor of R103 and R114 has a relationship of Rs=R103+R114, it is necessary that Rs>R103. However, the series heating element (resistance value Rs) that heats the paper P having a wider width than the heating element 54b3 requires more electric power than the heating element 54b3, and the resistance value of Rs is lower than that of R103. It is required to be a resistance value. Therefore, the resistance value Rs of the series heating element is first determined, and then the resistance value R103 of the heating element 54b3 is set to a value lower than the resistance value Rs. That is, the resistance value R103 of the heating element 54b3 is required to be set to a resistance value lower than the resistance value calculated from the required electric power, and the heating element 54b3 is inevitably set to exceed the specifications. When using the configuration of the third embodiment, it is necessary to consider this point and establish a sufficient protection system or the like for the heating element 54b3.

As described above, in the configuration in which the power supply path is switched by using the contact switch, it is possible to eliminate the life reduction due to electromagnetic noise emission from the contact switch and contact wear. In addition, the power control unit 97 can be made cheaper and smaller than in the second embodiment. As described above, according to the third embodiment, even when the heating element to be fed is switched using the contact switch, electromagnetic noise due to arc discharge is not emitted during the operation of the contact switch, and the life of the contact is not shortened due to wear of the contact. A device can be provided.

[Heater and power supply unit]
FIG. 10 shows the heater 54 and the power supply unit used in the heating device of the fourth embodiment. The length of the heating element 54b5, which is the second heating element, formed on the heater 54 in the longitudinal direction is the same as that of the heating element 54b3 of the heater 54 used in Examples 1 to 4. However, the difference is that the contacts to which the heating element 54b5 is connected are the contacts 54d2 and 54d4. The length and shape of the heating element 54b6, which is the third heating element, in the longitudinal direction (the shape divided into two) are the same as the heating element 54b4 of the heater 54 used in the third embodiment, but are connected. The different contacts are the contacts 54d2 and 54d3. The electromagnetic relay 57d, which is the third switching means, is an electromagnetic relay having an a-contact configuration, one end of which is connected to the contact 54d3 and the other end of which is connected to the second pole of the AC power supply 55 and the contact 54d4. ..

[Current supply path]
FIG. 11 shows three types of current paths to the heating element when the heater 54 and the power control section 97 of the fourth embodiment are used. The current when power is supplied from the AC power supply 55 to the heating element 54b1 flows through the route indicated by the thick line in FIG. The power supply from the AC power supply 55 to the heating element 54b1 is controlled by the triac 56a. When supplying power to the heating element 54b1, the electromagnetic relay 57d may be open or short-circuited.

The current when power is supplied from the AC power supply 55 to the heating elements 54b5 and 54b6 flows through the route indicated by the thick line in FIG. 11(b). At this time, the contact of the electromagnetic relay 57d having the a-contact configuration is set to the short-circuited state, and the current flows through the heating elements 54b5 and 54b6 in parallel. Hereinafter, the heating elements 54b5 and 54b6 connected in parallel may be referred to as parallel heating elements. As a result, the heating elements 54b5 and 54b6 both generate heat, and in the longitudinal direction of the heater 54, it can be regarded as one heating element corresponding to the sheet width of B5 size, for example. The power supply from the AC power supply 55 to the parallel heating elements of the heating elements 54b5 and 54b6 is controlled by the triac 56b.

The electric current when the electric power is supplied from the AC power supply 55 to the heating element 54b5 flows through the route shown by the thick line in FIG. At this time, the contact of the electromagnetic relay 57d having the a-contact configuration is set to the open state, and the triac 56b controls the power supply from the AC power supply 55 to the heating element 54b5. Since the contact impedance of the electromagnetic relay 57d having the a-contact configuration in the open state is sufficiently larger than that of the heating element 54b5, almost no current flows through the heating element 54b6, and only the heating element 54b5 can generate heat. Here, both ends of the electromagnetic relay 57d having an a-contact configuration are connected to both ends of a heating element 54b5 and a heating element 54b6 connected in series. Therefore, electromagnetic noise is not radiated during the operation of the electromagnetic relay 57a having the a-contact configuration as in the first embodiment, and contact wear (=life shortening) due to arc discharge does not occur.

In the configuration of the fourth embodiment, similarly to the third embodiment, there are restrictions on the resistance values of the heating elements 54b5 and 54b6. The resistance value of the heating element 54b5 is R116, and the resistance value of the heating element 54b6 is R117. The resistance value Rp of the parallel heating elements of the heating elements 54b5 and 54b6 has a relationship of 1/Rp=(1/R116)+(1/R117). If the resistance value R116 of the heating element 54b5 is set to 110Ω and the resistance value Rp of the parallel heating element is set to 90Ω, it is necessary to set the resistance value R117 of the heating element 54b6 to 495Ω. The heating element 54b6 needs to be made of a resistance material having a higher resistivity (specifically, about twice) than that of the heating element 54b5. As described above, the heater 54 used in the third and fourth embodiments has different restrictions imposed on the setting of the resistance value of the heating element. Therefore, it is desirable to select a means that matches the design conditions.

As described above, in the configuration in which the power supply path is switched by using the contact switch, it is possible to eliminate the life reduction due to electromagnetic noise emission from the contact switch and contact wear. As described above, according to the fourth embodiment, even when the heating element to be supplied with power is switched using the contact switch, electromagnetic noise due to arc discharge is not emitted during operation of the contact switch, and life reduction due to contact wear does not occur. A device can be provided.

54b1 to 54b3 Heat generating elements 54d1 to 54d4 Contact points 56a to 56c Bidirectional thyristor 57a Electromagnetic relay

Claims (27)

A heating device having a plurality of heating elements,
A first heating element,
A second heating element and a third heating element having a length in the longitudinal direction shorter than that of the first heating element;
A first contact to which one end of the first heating element is connected,
A second contact to which one end of the second heating element and one end of the third heating element are connected,
A third contact to which the other end of the third heating element is connected,
A fourth contact point to which the other end of the first heating element and the other end of the second heating element are connected,
A first switching means for connecting or disconnecting an electric path between the second contact and the fourth contact;
A heating device comprising: A substrate on which the plurality of heating elements are mounted,
Two first heating elements are arranged on both sides of the substrate in a direction orthogonal to the longitudinal direction,
The heating device according to claim 1, wherein one end of each of the two first heating elements is connected to the first contact, and the other end thereof is connected to the fourth contact. The heating device according to claim 2, wherein the second heating element and the third heating element are arranged in a region of the first heating element in the longitudinal direction of the substrate. First switch means for connecting one end to the first contact and for connecting the other end to a first pole of an AC power supply for controlling the supply of electric power to the first heating element;
Second switch means for controlling supply of electric power to the second heating element, one end of which is connected to the second contact and the other end of which is connected to the first pole;
Third switch means for controlling supply of electric power to the third heating element, one end of which is connected to the third contact and the other end of which is connected to the first pole;
The heating device according to any one of claims 1 to 3, further comprising: The first heating element is supplied with power through a power supply path via the first switch means, the first contact and the fourth contact, irrespective of the state of the first switching means,
The second heating element sets the first switching unit in the open state, and is supplied with power through a power supply path that passes through the second switching unit, the second contact, and the fourth contact,
The third heating element puts the first switching unit in the connection state, and is supplied with electric power through a power supply path that passes through the third switching unit, the second contact, and the third contact. The heating device according to claim 4, wherein: First switch means for connecting one end to the first contact and for connecting the other end to a first pole of an AC power supply for controlling the supply of electric power to the first heating element;
Second switch means for controlling the supply of electric power to the second heating element or the third heating element;
Second switching capable of switching between a state in which one end is connected to the second contact and the other end is connected to the second switch means and a state in which the other end is connected to the second pole of the AC power supply. Means and
Equipped with
The second switch means controls the supply of electric power to the second heating element when the other end of the second switch means is connected to the second switch means, and the second switch means 4. The supply of electric power to the third heating element is controlled when the other end of the means is connected to the second pole, and the third heating element is controlled according to any one of claims 1 to 3. Heating device. Regardless of the state of the second switching means, the first heating element is supplied with power through a power supply path that passes through the first switch means, the first contact point and the fourth contact point,
The second heating element is in a state where the other end of the second switching means is connected to the second switch means, and the second heating means, the second contact and the fourth contact are interposed. Power is supplied through the power supply path
In the third heating element, the other end of the second switching means is connected to the second pole of the AC power supply, and the second switching means, the second contact and the third The heating device according to claim 6, wherein electric power is supplied through a power supply path via the contact. 8. The length of the second heating element in the longitudinal direction is longer than the length of the third heating element in the longitudinal direction, according to any one of claims 4 to 7. Heating device. First switch means for connecting one end to the first contact and for connecting the other end to a first pole of an AC power supply for controlling the supply of electric power to the first heating element;
One end is connected to the third contact, the other end is connected to the first pole, and a second for controlling the supply of electric power to the second heating element and/or the third heating element. Switch means of
Equipped with
The second switch means controls the supply of electric power to a heating element in which the second heating element and the third heating element are connected in series when the first switching means is in the open state, The heating device according to any one of claims 1 to 3, wherein the first switching unit controls supply of electric power to the third heating element in the connected state. The heating device according to claim 9, wherein two of the second heating elements are arranged on both sides of the third heating element in a direction orthogonal to the longitudinal direction. Regardless of the state of the first switching means, the first heating element is supplied with power through a power supply path via the first switch means, the first contact and the fourth contact,
In the second heating element and the third heating element, the first switching means is in the open state, and power is supplied through the second switching means, the third contact and the fourth contact. Is powered by the route,
The third heating element puts the first switching means in the connection state and is supplied with electric power through a power supply path that passes through the second switching means, the second contact, and the third contact. The heating device according to claim 10, wherein: The length in the longitudinal direction of the area that generates heat when the second heating element and the third heating element are connected in series is the length of the area that generates heat in the third heating element in the longitudinal direction. The heating device according to any one of claims 9 to 11, which is longer than the length. The impedance when the first switching means is in the connected state is smaller than the impedance of the second heating element,
The impedance when the first switching unit is in the open state is larger than the impedance of the second heating element, any one of claims 4, 5, and 9 to 11. The heating device according to item 1. The impedance when the other end of the second switching means is connected to the second switching means is smaller than the impedance of the third heating element,
The impedance when the other end of the second switching unit is connected to the second pole is smaller than the impedance of the second heating element. Heating device. A heating device having a plurality of heating elements,
A first heating element,
A second heating element and a third heating element having a length in the longitudinal direction shorter than that of the first heating element;
A first contact to which one end of the first heating element is connected,
A second contact to which one end of the second heating element and one end of the third heating element are connected,
A third contact to which the other end of the third heating element is connected,
A fourth contact point to which the other end of the first heating element and the other end of the second heating element are connected,
Third switching means for bringing an electric path between the third contact and the fourth contact into a connected state or an open state;
A heating device comprising: A substrate on which the plurality of heating elements are mounted,
Two first heating elements are arranged on both sides of the substrate in a direction orthogonal to the longitudinal direction,
The heating device according to claim 15, wherein one end of each of the two first heating elements is connected to the first contact and the other end is connected to the fourth contact. The heating device according to claim 16, wherein the second heating element and the third heating element are arranged in a region of the first heating element in the longitudinal direction of the substrate. First switch means for connecting one end to the first contact and for connecting the other end to a first pole of an AC power supply for controlling the supply of electric power to the first heating element;
One end is connected to the second contact, the other end is connected to the first pole, and a second for controlling the supply of electric power to the second heating element and/or the third heating element. Switch means of
Equipped with
The second switch means controls the supply of electric power to a heating element in which the second heating element and the third heating element are connected in parallel when the third switching means is in the connection state, The heating device according to any one of claims 15 to 17, wherein the third switching unit controls supply of electric power to the second heating element in the open state. The heating device according to claim 18, wherein two of the third heating elements are arranged on both sides of the second heating element in a direction orthogonal to the longitudinal direction. The first heating element is supplied with power through a power supply path via the first switch means, the first contact and the fourth contact, regardless of the state of the third switching means,
The second heating element and the third heating element have the first switching means in the connection state, and the second switching means, the second contact, the third contact, and the fourth Power is supplied through the power supply path through the contacts,
The second heating element sets the first switching means to the open state and is supplied with electric power through a power supply path that passes through the second switching means, the second contact and the fourth contact. The heating device according to claim 19, wherein: When the second heating element and the third heating element are connected in parallel, the length in the longitudinal direction of the area where the second heating element generates heat is the length in the longitudinal direction of the area where the second heating element generates heat. 21. The heating device according to claim 18, wherein the heating device is longer than the length. The impedance when the third switching means is in the connected state is smaller than the impedance of the second heating element,
22. The heating device according to claim 21, wherein the impedance when the third switching unit is in the open state is larger than the impedance of the second heating element. A fixing device, which fixes a toner image on a recording material by the heating device according to any one of claims 1 to 22. A first rotating body heated by the plurality of heating elements;
A second rotating body that forms a nip portion with the first rotating body;
The fixing device according to claim 23, further comprising: The fixing device according to claim 24, wherein the first rotating body is a film. The plurality of heating elements are provided so as to contact the inner surface of the film,
26. The fixing device according to claim 25, wherein the nip portion is formed by the second rotating body via the film. An image forming means for forming a toner image on the recording material,
A fixing device according to any one of claims 23 to 26,
An image forming apparatus comprising:

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